On sobota 8. května 2021 12:26:36 CEST Oleksandr Natalenko wrote:
> Hello.
>
> On Thu, May 06, 2021 at 07:30:01PM -0700, Jesse Brandeburg wrote:
> > Oleksandr brought a bug report where netpoll causes trace messages in
> > the log on igb.
> >
> > [22038.710800] ------------[ cut here ]------------
> > [22038.710801] igb_poll+0x0/0x1440 [igb] exceeded budget in poll
> > [22038.710802] WARNING: CPU: 12 PID: 40362 at net/core/netpoll.c:155
> > netpoll_poll_dev+0x18a/0x1a0
> >
> > After some discussion and debug from the list, it was deemed that the
> > right thing to do is initialize the clean_complete variable to false
> > when the "netpoll mode" of passing a zero budget is used.
> >
> > This logic should be sane and not risky because the only time budget
> > should be zero on entry is netpoll. Change includes a small refactor
> > of local variable assignments to clean up the look.
> >
> > Fixes: 16eb8815c235 ("igb: Refactor clean_rx_irq to reduce overhead and
> > improve performance") Reported-by: Oleksandr Natalenko
> > <[email protected]>
> > Suggested-by: Alexander Duyck <[email protected]>
> > Signed-off-by: Jesse Brandeburg <[email protected]>
> > Reviewed-by: Alexander Duyck <[email protected]>
> > ---
> >
> > Compile tested ONLY, but functionally it should be exactly the same for
> > all cases except when budget is zero on entry, which will hopefully fix
> > the bug.
> >
> > Sending this through intel-wired-lan with Alex's ACK.
> > ---
> >
> > drivers/net/ethernet/intel/igb/igb_main.c | 12 ++++++++----
> > 1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> > b/drivers/net/ethernet/intel/igb/igb_main.c index
> > 0cd37ad81b4e..b0a9bed14071 100644
> > --- a/drivers/net/ethernet/intel/igb/igb_main.c
> > +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> > @@ -7991,12 +7991,16 @@ static void igb_ring_irq_enable(struct
> > igb_q_vector *q_vector)>
> > **/
> >
> > static int igb_poll(struct napi_struct *napi, int budget)
> > {
> >
> > - struct igb_q_vector *q_vector = container_of(napi,
> > - struct igb_q_vector,
> > - napi);
> > - bool clean_complete = true;
> > + struct igb_q_vector *q_vector;
> > + bool clean_complete;
> >
> > int work_done = 0;
> >
> > + /* if budget is zero, we have a special case for netconsole, so
> > + * make sure to set clean_complete to false in that case.
> > + */
> > + clean_complete = !!budget;
> > +
> > + q_vector = container_of(napi, struct igb_q_vector, napi);
> >
> > #ifdef CONFIG_IGB_DCA
> >
> > if (q_vector->adapter->flags & IGB_FLAG_DCA_ENABLED)
> >
> > igb_update_dca(q_vector);
>
> This didn't fix the issue neither for me, nor for another person from
> the kernel bugzilla [1].
>
> The same printout still happens:
>
> ```
> May 07 20:26:55 spock kernel: igb_poll+0x0/0x1440 [igb] exceeded budget in
> poll May 07 20:26:55 spock kernel: WARNING: CPU: 13 PID: 12285 at
> net/core/netpoll.c:154 netpoll_poll_dev+0x18a/0x1a0 …
> May 07 20:26:55 spock kernel: Call Trace:
> May 07 20:26:55 spock kernel: netpoll_send_skb+0x1a0/0x260
> May 07 20:26:55 spock kernel: write_msg+0xe5/0x100 [netconsole]
> May 07 20:26:55 spock kernel: console_unlock+0x42f/0x720
> May 07 20:26:55 spock kernel: suspend_devices_and_enter+0x2ac/0x7f0
> May 07 20:26:55 spock kernel: pm_suspend.cold+0x321/0x36c
> May 07 20:26:55 spock kernel: state_store+0xa6/0x140
> May 07 20:26:55 spock kernel: kernfs_fop_write_iter+0x124/0x1b0
> May 07 20:26:55 spock kernel: new_sync_write+0x16a/0x200
> May 07 20:26:55 spock kernel: vfs_write+0x223/0x2e0
> May 07 20:26:55 spock kernel: __x64_sys_write+0x6d/0xf0
> ```
>
> Probably, your patch is still fine, but another idea is desperately
> needed :).
>
> Thanks.
>
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=212573
Gentle ping. IIUC, the patch was not picked up anyway, but maybe there's
another idea?
Thanks.
--
Oleksandr Natalenko (post-factum)